The primary goals of this project are the development of quantitative physical models for the demineralization and remineralization of tooth enamel and the application of these models to the design and optimization of therapies for caries prevention. The project seeks to firmly establish a quantitative understanding of the relationship of the kinetics of demineralization and remineralization of blocks of enamel to the kinetics of these processes as observed in suspensions of hydroxyapatite crystals. This entails three separate lines of investigation: suspension studies, block enamel studies and correlative studies. The suspension studies carried out using pH and ion selective electrode stats to maintain constant solution composition in the reaction vessel, with a microcomputer recording the quantities of reagents added to do so. The block enamel studies consist of demineralization, remineralization and subsequent acid challenge procedures. After these procedures profiles of both composition and mineral density are determined. In studies where such analyses are done at several different time points, a computational technique developed in this project is used to construct a detailed history of the time course of the experiment in terms of solution composition and ion activity profiles in the enamel. Correlations between block enamel and suspension experiments are established via calculations in which the enamel is assumed to be a matrix of hydroxyapatite crystals. Appropriate mathematics have been developed which account for the time course of the diffusion and crystal dissolution processes along with constraints of instantaneous chemical equilibrium and charge balance. The above results are used in the design and optimization of a two component fluoride delivery system in which a solid organic acid provides a demineralization pretreatment such that subsequent remineralization using calcium fluoride as a controlled release fluoride source is maximal.